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More recent concerns about supposed dysgenic effects in human populations were advanced by the controversial psychologist and self-described "scientific racist" [5] Richard Lynn, notably in his 1996 book Dysgenics: Genetic Deterioration in Modern Populations, which argued that changes in selection pressures and decreased infant mortality since ...
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Genetic purging is the increased pressure of natural selection against deleterious alleles prompted by inbreeding. [1]Purging occurs because deleterious alleles tend to be recessive, which means that they only express all their harmful effects when they are present in the two copies of the individual (i.e., in homozygosis).
The incidental purging of non-deleterious alleles due to such spatial proximity to deleterious alleles is called background selection. [4] This effect increases with lower mutation rate but decreases with higher recombination rate. [5] Purifying selection can be split into purging by non-random mating (assortative mating) and purging by genetic ...
Beneficial nonsense mutations increase the overall fitness and reproductive success of an organism, opposite of the effects of a deleterious mutation. [ 2 ] [ 8 ] Because a nonsense mutation introduces a premature stop codon within a sequence of DNA, it is extremely unlikely that this scenario can actually benefit the organism. [ 1 ]
This means that beneficial alleles are more likely to become fixed, whereas deleterious alleles are more likely to be lost. In populations that are shrinking in size, selection coefficients are not as effective. Thus, there is a higher probability of beneficial alleles being lost and deleterious alleles being fixed.
Illustration of chromosome crossover during genetic recombination. In evolutionary genetics, Muller's ratchet (named after Hermann Joseph Muller, by analogy with a ratchet effect) is a process which, in the absence of recombination (especially in an asexual population), results in an accumulation of irreversible deleterious mutations.
A contronym is alternatively called an autantonym, auto-antonym, antagonym, [3] [4] enantiodrome, enantionym, Janus word (after the Roman god Janus, who is usually depicted with two faces), [4] self-antonym, antilogy, or addad (Arabic, singular didd).